Device and method for detecting touch screen

ABSTRACT

The invention discloses a full screen driven detection. A driving signal is simultaneously provided to all first conductive strips arranged in parallel in a first direction in a touch screen, and mutual capacitive signals are detected from all second conductive strips arranged in parallel in a second direction. The mutual capacitive signals can be used for determining whether an external conductive object coupled to the ground is touching or approaching the touch screen or not even if water or other conductive object not coupled to ground is on the touch screen. Thus, the baseline of the mutual capacitive signals can be updated if the touch screen is not touched or approached by any external conductive object coupled to ground over a predetermined period of time.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This patent application claims the domestic priority of the U.S.provisional applications 61/547,186 filed on Oct. 14, 2011 and61/577,181 filed on Dec. 19, 2011. This patent application is also acontinuation-in-part of the U.S. patent application Ser. No. 12/407,100filed on May 19, 2009, which claims the foreign priority of Taiwanpatent applications TW097109691 filed on May 19, 2008 and TW098100567filed on Jan. 9, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a capacitive touch screen, and moreparticularly, a capacitive touch screen that avoids misjudgment due towater thereon.

2. Description of the Prior Art

A conventional mutual capacitive sensor includes an insulating surfacelayer, a first conductive layer, a dielectric layer, a second conductivelayer. The first conductive layer and the second conductive layer have aplurality of first conductive strips and a plurality of secondconductive strips, respectively. Each of these conductive strips can bemade up by a plurality of conductive pads and connecting lines connectedto the conductive pads in series.

In the process of mutual capacitive detection, one of the firstconductive layer and the second conductive layer is driven, while theother of the first conductive layer and the second conductive layer isdetected. For example, a driving signal is sequentially provided to eachfirst conductive strip, and corresponding to each first conductive stripprovided with the driving signal, signals from all of the secondconductive strips are detected, which represent capacitive couplingsignals at the intersections between the first conductive strip providedwith the driving signal and all the second conductive strips. As aresult, capacitive coupling signals at the intersections between all thefirst and second conductive strips are obtained to form an image ofcapacitive values.

The image of capacitive values at the time when there is no externaltouches is obtained as a reference. By comparing the difference betweenthe reference image and the image of capacitive values later detected,the touch or approach of an external conductive object can bedetermined, and furthermore, the position touched or approached by theexternal conductive object can be determined.

However, if a conductive substance crosses over at least two conductivestrips on the insulating surface layer, even when there is no touch orapproach by any external conductive object, the image of capacitivevalues may change as a result of capacitive coupling between theconductive substance and the conductive strips, leading to misjudgments.For example, a water stain crossing more than two conductive strips onthe insulating surface layer may cause changes in the image ofcapacitive values, and may be mistaken as the pressing of a finger.

From the above it is clear that prior art still has shortcomings. Inorder to solve these problems, efforts have long been made in vain,while ordinary products and methods offering no appropriate structuresand methods. Thus, there is a need in the industry for a novel techniquethat solves these problems.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a full screen drivendetection by simultaneously providing a driving signal to conductivestrips arranged in parallel in a first direction in a touch screen, anddetecting mutual capacitive signals on conductive strips arranged inparallel in a second direction, thereby determining whether there is anapproach or a touch of an external conductive object that is coupled toground. The approach or the touch of an external conductive objectcoupled to ground can be determined even if a water stain or otherconductive object that is not coupled to ground is on the touch screen.Thus, when the touch screen is not touched or approached by any externalconductive object over a period of time, the baseline of the mutualcapacitive signals can be updated.

The above and other objectives of the present invention can be achievedby the following technical scheme. A device for detecting a touch screenprovided by the present invention includes: the touch screen including aplurality of first conductive strips and a plurality of secondconductive strips; and a controller for performing a full screen drivendetection, including: simultaneously providing a driving signal to allof the first conductive strips; when all of the first conductive stripsare provided with the driving signal, detecting mutual capacitivesignals of all of the second conductive strips to generate aone-dimensional (1D) sensing information based on the signals of all ofthe second conductive strips; and determining whether at least oneexternal conductive object coupled to ground is touching or approachingthe touch screen based on the 1D sensing information; and when thecontroller determining the touch screen is not touched or approached byany external conductive object over a predetermined period of time basedon the 1D sensing information, performing a 2D mutual capacitivedetection to obtain a 2D sensing information to update reference valuesbased on the 2D sensing information, wherein the 2D mutual capacitivedetection includes: sequentially providing a driving signal to one ormore different conductive strips in the first conductive strips, andproviding a DC potential to all of the guarding conductive strips; eachtime one or more different conductive strips in the first conductivestrips being provided with the driving signal, detecting the signals ofall of the second conductive strips to obtain a 1D sensing informationcorresponding to the one or more first conductive strips being providedwith the driving signal generated based on the mutual capacitive signalsof all of the second conductive strips; and combining each 1D sensinginformation corresponding to the one or more first conductive stripsbeing provided with the driving signal to generate a 2D sensinginformation.

The above and other objectives of the present invention can also beachieved by the following technical scheme. A method for detecting atouch screen in accordance with the present invention includes:providing the touch screen including a plurality of first conductivestrips and a plurality of second conductive strips; performing a fullscreen driven detection including: simultaneously providing a drivingsignal to all of the first conductive strips; when all of the firstconductive strips are provided with the driving signal, detecting mutualcapacitive signals of all of the second conductive strips to generate aone-dimensional (1D) sensing information based on the signals of all ofthe second conductive strips; and determining whether at least oneexternal conductive object coupled to ground is touching or approachingthe touch screen based on the 1D sensing information; and whendetermining the touch screen is not touched or approached by anyexternal conductive object over a predetermined period of time based onthe 1D sensing information, performing a 2D mutual capacitive detectionto obtain a 2D sensing information, and updating reference values basedon the 2D sensing information, wherein the 2D mutual capacitivedetection includes: sequentially providing a driving signal to one ormore different conductive strips in the first conductive strips; eachtime one or more different conductive strips in the first conductivestrips being provided with the driving signal, detecting the signals ofall of the second conductive strips to obtain a 1D sensing informationcorresponding to the one or more first conductive strips being providedwith the driving signal generated based on the mutual capacitive signalsof all of the second conductive strips; and combining each 1D sensinginformation corresponding to the one or more first conductive stripsbeing provided with the driving signal to generate a 2D sensinginformation.

By employing the above technical schemes, the present invention includesat least the following advantages and beneficial effects:

1. Full screen driven detection can determine an approach or a touch ofan external conductive object coupled to ground regardless of whetherany water stain or other conductive object that is not coupled to groundis on the touch screen, and can further perform an update of referencevalues when knowing for sure that no approach or touch of any externalconductive object coupled to ground is present on the screen; and

2. Full screen driven detection is more time and power saving comparedto 2D mutual capacitive detection, thus more suitable for determiningwhether a power-saving mode should be entered.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thefollowing detailed description of the preferred embodiments, withreference made to the accompanying drawings, wherein:

FIGS. 1A and 1B are schematic diagrams depicting a position detectingdevice;

FIGS. 1C to 1F are schematic diagrams depicting the structure of asensing layer;

FIGS. 2A and 2B are schematic diagrams depicting a capacitive touchscreen including guarding conductive strips;

FIG. 2C is a schematic diagram illustrating a 2D mutual capacitivedetection;

FIG. 2D is a schematic diagram illustrating a full screen drivendetection;

FIG. 2E is a flowchart illustrating performing a full screen drivendetection before performing a 2D mutual capacitive detection proposed inaccordance with a first embodiment of the present invention;

FIG. 3 is a flowchart illustrating determining locations based onresults of a full screen driven detection and a 2D mutual capacitivedetection proposed in accordance with a second embodiment of the presentinvention;

FIG. 4A to 4C are flowcharts illustrating determining locations based onresults of a full screen driven detection and a mutual capacitivedetection in accordance with a third embodiment of the presentinvention;

FIG. 5A is a flowchart illustrating a way of updating reference valuesproposed in accordance with a fourth embodiment of the presentinvention; and

FIG. 5B is a flowchart illustrating a way of updating reference valuesaccording to a fifth embodiment of the present invention;

FIG. 6 is a flowchart illustrating a method for communication throughtouch screens according to a sixth embodiment of the present invention;and

FIG. 7 is a schematic diagram depicting performing communication usingtouch screens proposed by a seventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments of the present invention are described in detailsbelow. However, in addition to the descriptions given below, the presentinvention can be applicable to other embodiments, and the scope of thepresent invention is not limited by such, rather by the scope of theclaims. Moreover, for better understanding and clarity of thedescription, some components in the drawings may not necessary be drawnto scale, in which some may be exaggerated relative to others, andirrelevant parts are omitted.

Referring to FIG. 1A, the present invention provides a positiondetecting device 100, which includes a touch screen 120 and adriving/detecting unit 130. The touch screen 120 has a sensing layer. Inan example of the present invention, the sensing layer may include afirst sensing layer 120A and a second sensing layer 120B. The first andsecond sensing layers 120A and 120B each has a plurality of conductivestrips 140, wherein the first conductive strips 140A of the firstsensing layer 120A and the second conductive strips 140B of the secondsensing layer 120B overlap each other. In another example of the presentinvention, the first and second conductive strips 140A and 140B aredisposed on a co-planar sensing layer. The driving/detecting unit 130produces sensing information based on signals of the conductive strips140. In the case of self-capacitive detection, for example, conductivestrips 140 that are being driven are detected. In the case ofmutual-capacitive detection, a portion of the conductive strips 140 thatare not being directly driven by the driving/detecting unit 130 aredetected. In addition, the touch screen 120 can be disposed on a display110. An optional shielding layer (not shown) can be interposed betweenthe touch screen 120 and the display 110. In a preferred example of thepresent invention, no shielding layer is provided between the touchscreen 120 and the display 110 so as to reduce the thickness of thetouch screen 120.

The position detecting device 100 of the present invention can beapplied to a computer system as shown in FIG. 1B, which includes acontroller 160 and a host 170. The controller includes thedriving/detecting unit 130 to operatively couple the touch screen 120(not shown). In addition, the controller 160 may include a processor 161for controlling the driving/detecting unit 130 in generating the sensinginformation. The sensing information can be stored in a memory 162 andaccessible by the processor 161. Moreover, the host 170 constitutes themain body of the computer system, and primarily includes a centralprocessing unit 171, a storage unit 173 that can be accessed by thecentral processing unit 171, and the display 110 for displaying resultsof operations.

In another example of the present invention, a transmission interface isincluded between the controller 160 and the host 170. The controllingunit transmits data to the host via the transmission interface. One withordinary skill in the art can appreciate that the transmission interfacemay include, but not limited to, UART, USB, I2C, Bluetooth, Wi-Fi, IRand other wireless or wired transmission interfaces. In an example ofthe present invention, data transmitted can be positions (e.g.coordinates), identification results (e.g. gesture codes), commands,sensing information or other information that can be provided by thecontroller 160.

In an example of the present invention, the sensing information can beinitial sensing information generated under the control of the processor161, and this information is passed onto the host 170 for analysis, suchas position analysis, gesture determination, command identification etc.In another example of the present invention, the sensing information canbe analyzed by the processor 161 first before forwarding the determinedpositions, gestures, commands, or the like to the host 170. The presentinvention includes but is not limit to this example, and one withordinary skill in the art can readily appreciate other interactionsbetween the controller 160 and the host 170.

Referring to FIG. 1C, a pattern of a capacitive touch screen is shown,which includes a plurality of conductive pads and a plurality ofconnecting lines. These connecting lines include a plurality of firstconnecting lines and a plurality of second connecting lines. These firstconnecting lines are arranged in a first direction (e.g. one of thehorizontal and vertical directions) and are connected to a portion ofthese conductive pads to form a plurality of conductive strips arrangedin the first direction. Similarly, these second connecting lines arearranged in a second direction (e.g. the other one of the horizontal andvertical directions) and are connected to another portion of theseconductive pads to form a plurality of conductive strips arranged in thesecond direction.

These conductive strips (the first and second conductive strips) can bemade of transparent or opaque materials, such as transparent Indium TinOxide (ITO). In terms of the structure, it can be categorized intoSingle ITO (SITO) structure and Double ITO (DITO) structure. One withordinary skill in the art can appreciate that other materials can beused as the conductive strips, such as carbon nano tube, and they willnot be further described.

In an example, the vertical direction is regarded as the firstdirection, while the horizontal direction is regarded as the seconddirection. Thus, the vertical conductive strips are the first conductivestrips, and the horizontal conductive strips are the second conductivestrips. However, one with ordinary skill in the art can appreciate thatthe above is merely an example of the present invention, and the presentinvention is not limited to this. For example, the horizontal directioncan be regarded as the first direction, while the vertical direction canbe regarded as the second direction. In addition, the number of thefirst and the second conductive strips can be the same or different. Forexample, there may be N first conductive strips and M second conductivestrips.

FIG. 1E is a cross-sectional diagram of FIG. 1C along a line I-I, whichshows an insulating substrate 17, a portion of a second conductive strip(including a conductive pad 11, a second connecting line 12, and aconductive pad 13), an insulating layer 18, a portion of a firstconductive strip (including a first connecting line 15), and aninsulating surface layer 19. In an example of the present invention, thesubstrate 17, the insulating layer 18, and the insulating surface layer19 can be made of transparent or opaque materials, such as glass or aplastic film. One with ordinary skill in the art can appreciate otherconstructions of the present example, and they will not be furtherdescribed.

In an example of the present invention, FIG. 1D is a cross-sectionaldiagram of FIG. 1C along a line II-II, illustrating the structure of aDITO capacitive touch screen. It includes a substrate 17, a portion of asecond conductive strip (including a second connecting line 12), aninsulating layer 18, a portion of a first conductive strip (including aconductive pad 14, a first connecting line 15, and a conductive pad 16),and an insulating surface layer 19. In other words, in an example of thepresent invention, the capacitive touch screen includes an insulatingsurface layer, a first sensing layer of the first conductive strips, aninsulating layer, and a second sensing layer of the second conductivestrips. In another example of the present invention, the capacitivetouch screen may be a rectangle having two opposite long sides and twoopposite short sides, wherein the first conductive strips are arrangedin parallel with the two opposite short sides, while the secondconductive strips are arranged in parallel with the two opposite longsides.

In an example of the present invention, FIG. 1F is a cross-sectionaldiagram of FIG. 1C along the line I-I, illustrating the structure of aSITO capacitive touch screen. It includes a substrate 17, a portion of asecond conductive strip (including a second connecting line 12), aninsulating layer 18, a portion of a first conductive strip (including aconductive pad 14, a first connecting line 15, and a conductive pad 16),and an insulating surface layer 19. The conductive pads 14 and 15 of thefirst conductive strip and the second connecting line 12 of the secondconductive strip are co-planar, and the first connecting line 15 bridgesover the second connecting line 12. The first connecting line 15 isisolated from the second connecting line 12 by the insulating layer 18.One with ordinary skill in the art can appreciate other types ofbridging, for example, instead of the “over-bridge” structure as shownin the present example, an “under-bridge” structure can be formed.

Guarding or shielding conductive strips can also be interposed betweenthe first and second conductive strips. The guarding conductive stripscan increase the amount of change in the detected mutual capacitivesignals and also reduce noises from external conductive objects as wellas phantom (unreal) touches resulting from signals flowing from thecapacitive touch screen to external conductive objects and back into thecapacitive touch screen again. When the guarding conductive strips areinterposed between the first and second conductive strips, and theguarding conductive strips are provided with a DC current or coupled tosystem ground, the guarding conductive strips can shield any capacitivecoupling directly between the first and the second conductive strips, sothat the amount of change in mutual capacitive signals that can beinfluenced by any external conductive object coupled to ground isincreased.

For example, as shown in FIGS. 2A and 2B, schematic diagrams depicting acapacitive touch screen including the guarding conductive strips areshown. Guarding conductive strips 21 and first conductive strips 23intersect and exposed from each other, and each first conductive strip23 includes a plurality of openings 24 for exposing conductive pads 25of second conductive strips 22.

Referring now to FIG. 2C, in the process of two-dimension (2D) mutualcapacitive detection, an alternating driving signal (e.g. a pulse widthmodulated (PWM) signal) is sequentially provided to each of the firstconductive strips 23, and one-dimension (1D) sensing information of eachconductive strip provided with the driving signal can be obtained viasignals S of the second conductive strips 22. Sensing informationcorresponding to all of the first conductive strips 23 is then combinedto construct 2D sensing information. The 1D sensing information can begenerated by the signals of the second conductive strips 22, or based ondifferences between the signals of the second conductive strips 22 andsome reference values. Furthermore, the sensing information can begenerated based on current, voltage, capacitive coupling quantity,charge quantity, or other electrical characteristics of the signals, andcan be in analog or digital form. In this example, the driving signal isprovided in turn to one of the first conductive strips 23. One withordinary skill in the art can appreciate that the driving signal canalso be provided to two or more adjacent strips of the first conductivestrips 23 at a time.

For example, in an example of the present invention, a driving signal isprovided in turn to one of the first conductive strips, and when each ofthe first conductive strips is being provided with the driving signal,1D sensing information of the first conductive strip being provided withthe driving signal is obtained via signals generated by all of thesecond conductive strips. Sensing information corresponding to all ofthe first conductive strips is then combined to construct 2D sensinginformation. In another example of the present invention, a drivingsignal is sequentially provided to a pair of the first conductivestrips, and when each pair of the first conductive strips is beingprovided with the driving signal simultaneously, 1D sensing informationof the first conductive strips being provided with the driving signal isobtained via signals generated by all of the second conductive strips.Sensing information corresponding to each pair of the first conductivestrips is then combined to construct 2D sensing information.

One with ordinary skill in the art can appreciate that the location ofeach external conductive object coupled to ground can be determinedbased on the 2D sensing information. For example, a range in which eachexternal conductive object coupled to ground touches or approaches canbe first determined by methods such as watershed algorithm, objectconnecting method, or other image segmentation methods. Then, the exactlocation is determined. For example, signal values of the range in whichthe external conductive object touches or approaches can be used tocalculate the centroid position.

When there is no external conductive object actually approaching ortouching the touch screen, or no touch or approach by externalconductive objects is determined by the system, the position detectingdevice may generate reference values based on the signals of the secondconductive strips. The sensing information can be generated based on thesignals of the second conductive strips or by subtracting the referencevalues from the signals of the second conductive strips. In the formercase, real or unreal touches can be determined by the differencesbetween the sensing information and the reference values. In the lattercase, which is a preferred example of the present invention, the sensinginformation itself is already the differences that can be used directlyto determine real or unreal touches. The reference values can beobtained at the initial phase of the position detective device orrepeatedly obtained in the operational phase of the position detectingdevice.

In the following descriptions, when an external conductive objectapproaches or covers the touch screen and causes a real touch, the partof the sensing information corresponding to the real touch is calledreal-touch sensing information. On the contrary, the part of the sensinginformation that exhibits opposite characteristics to the real-touchsensing information is called unreal-touch sensing information, whichrepresents an unreal touch. The formation of real-touch sensinginformation is not necessarily entirely due to an approach or coverageon the touch screen by an external conductive object, but an approach orcoverage on the touch screen by an external conductive object is merelyone of the causes for a real touch. Said sensing information may includebut not limited to 1D sensing information or 2D sensing information.Moreover, the formation of an unreal touch does not necessarily meansthe existence of an external conductive object or any substances at thecorresponding location. Furthermore, real-touch sensing information maybe one that conforms or is similar to the sensing information caused bya real touch, and not necessarily caused by an actual externalconductive object approaching or covering the touch screen. For example,when 1D sensing information exhibits signal values of the conductivestrips, real-touch sensing information may be positive values that firstincrease then decrease, or negative values that first decrease thenincrease; whereas unreal-touch sensing information is opposite to thereal-touch sensing information. As another example, 1D sensinginformation exhibits differences between one conductive strip andanother conductive strip, real-touch sensing information may be positivevalues that first increase then decrease plus negative values that firstdecrease then increase, that is, positive values followed by negativevalues; whereas unreal-touch sensing information is opposite to thereal-touch sensing information.

When a conductive substance such as water is adhered to the insulatingsurface layer, sensing information may vary with the area of the adheredconductive substance. When the area in which the conductive substanceadhered is smaller, the capacitive coupling between the conductivesubstance and the conductive strips may exhibit unreal-touch sensinginformation. However, when the area in which the conductive substanceadhered is larger, the capacitive coupling between the conductivesubstance and the conductive strips may exhibit not only unreal-touchsensing information, but also real-touch sensing information. When watercovers many regions, numerous real-touch sensing information andunreal-touch sensing information may be generated, causing misjudgment.

If the sensing information exhibits only unreal-touch sensinginformation but no real-touch sensing information, it can be determinedthat a conductive substance is adhered to the insulating surface layer.In addition, if the sensing information has unreal-touch sensinginformation as well as real-touch sensing information at the edge of theunreal-touch sensing information, it can also be determined that aconductive substance is adhered to the insulating surface layer. When itis determined that conductive substance is adhered to the insulatingsurface layer, the touch sensor may notify the system or a user of thefact that a conductive substance is adhered to the insulating surfacelayer, and wait for further actions to be taken. For example, the touchsensor may stop updating the reference values or not provide locationsof any detected external conductive objects until the conductivesubstance is removed. However, the above circumstances are only limitedto a small area in which the conductive substance is adhered.

Furthermore, the present invention proposes a one dimensional mutualcapacitive detection with full screen driving (or simply referred to asfull screen driven detection hereinafter). Referring to FIG. 2D, in apreferred example of the present invention, the position detectingdevice must have the ability to provide a driving signal to all of thefirst conductive strips simultaneously. In the following, providing adriving signal (e.g. a PWM signal) to all of the first conductive stripssimultaneously is referred to as full screen driving. In each fullscreen driving, at least one 1D sensing information is produced based onsignals of all or part of the conductive strips. As mentioned before,one dimensional mutual capacitive detection with full screen drivingalso has its reference values. In addition, when touch screen includesthe guarding conductive strips 21, full screen driving further includessimultaneously driving all of the guarding conductive strips 21, i.e.,simultaneously providing a driving signal to all of the first conductivestrips 23 and the guarding conductive strips 21. In the followingdescriptions, during full screen driven detection, simultaneouslyproviding a driving signal to all of the first conductive strips 23 alsoimplies simultaneously providing a driving signal to all of the guardingconductive strips 21. If the touch screen includes the first conductivestrips 23 and the second conductive strips 22, but not the guardingconductive strips, then full screen driving only includes simultaneouslyproviding a driving signal to all of the first conductive strips.

If only a single conductive strip is provided with the driving signal,then the driving signal may cause unreal or real touch due to anattached conductive substance coupled to other conductive strips. Whenall of the first conductive strips in the full screen are provided withthe driving signal simultaneously, then the potentials for each firstconductive strip are the same, and the above problem will not occur.

Furthermore, when all of the first conductive strips in the full screenare provided with the driving signal simultaneously, an approach orcoverage of an external conductive object will exhibit real-touchsensing information, which can be used to determine the approach orcoverage of the external conductive object, the conductive stripapproached or covered by the external conductive object, and/or a 1Dcoordinate for the approach or touch of the external conductive object.

For example, a driving signal is simultaneously provided to all of thefirst conductive strips, and when the driving signal is simultaneouslyprovided to all of the first conductive strips, signals of all secondconductive strips are detected, forming 1D sensing informationconstructed by the signals of all of the second conductive strips. Wheneach value of the 1D sensing information represents the signal of onethe second conductive strips, a threshold value can be used to determineif there is at least one value in the 1D sensing information thatexceeds the threshold value. If so, then it indicates that at least oneexternal conductive object coupled to ground is touching or approachingthe touch screen.

In an example of the present invention, when the touch screen includesthe above guarding conductive strips, and when a full screen drivendetection is performed, the driving signal is simultaneously provided tothe guarding conductive strips and the first conductive strips. When a2D mutual capacitive detection is performed, and when a driving signalis provided, the guarding conductive strips are simultaneously providedwith a DC current or coupled to system ground.

For example, a device for detecting a touch screen in accordance withthe present invention includes: the touch screen including a pluralityof first conductive strips, a plurality of second conductive strips, anda plurality of guarding conductive strips, wherein the first conductivestrip, the second conductive strips, and the guarding conductive stripsare exposed and separated from each other; a controller for performing afull screen driven detection, which includes: simultaneously providing adriving signal to all of the first conductive strips and all of theguarding conductive strips; when all of the first conductive strips andall of the guarding conductive strips are provided with the drivingsignal, detecting mutual capacitive signals of all of the secondconductive strips to generate a one-dimensional (1D) sensing informationbased on the signals of all of the second conductive strips; anddetermining whether at least one external conductive object coupled toground is touching or approaching the touch screen based on the 1Dsensing information; and when the controller determining the touchscreen is touched or approached by at least one external conductiveobject coupled to ground based on the 1D sensing information, performinga 2D mutual capacitive detection to obtain a 2D sensing information todetermine a location of each external conductive object coupled toground based on the 2D sensing information, wherein the 2D mutualcapacitive detection includes: sequentially providing a driving signalto one or more different conductive strips in the first conductivestrips, and providing a DC potential to all of the guarding conductivestrips; each time one or more different conductive strips in the firstconductive strips being provided with the driving signal, detecting thesignals of all of the second conductive strips to obtain a 1D sensinginformation corresponding to the one or more first conductive stripsbeing provided with the driving signal generated based on the mutualcapacitive signals of all of the second conductive strips; and combiningeach 1D sensing information corresponding to the one or more firstconductive strips being provided with the driving signal to generate a2D sensing information.

In addition, the 1D sensing information can be generated by differentialvalues or dual differential values. For example, when each value of the1D sensing information represents the difference in signals of a pair ofsecond conductive strips, it can be determined whether there is at leastone zero-crossing between an adjacent positive value and an adjacentnegative value in the 1D sensing information. If there is at least onezero-crossing, then it indicates that at least one external conductiveobject coupled to ground is touching or approaching the touch screen.The adjacent positive value and adjacent negative value means that thereis no other value or only zero value(s) between that positive value andthat negative value. Furthermore, in an example of the presentinvention, values falling within a predetermined zero-value range areregarded as zero values, wherein the zero-value range includes zero.Since capacitive touch screen detection is vulnerable to external noiseinterference, using a zero-value range can reduce misjudgment andsimplify data. In an example of the present invention, assuming that thesignals of the second conductive strips are S₁, S₂ . . . and S_(n),respectively, and the 1D sensing information employs differentialvalues, then the values of the 1D sensing information are S₁-S₂, S₂-S₃ .. . and S_(n-1)-S_(n).

When each value of the 1D sensing information represents the differencebetween the signal differences of two pairs of the second conductivestrips, a threshold value can be used to determine if there is at leastone value in the 1D sensing information that exceeds the thresholdvalue. If so, then it indicates that at least one external conductiveobject coupled to ground is touching or approaching the touch screen.Alternatively, it can be determined if there is at least one valuebetween two zero-crossings that exceeds a threshold value. If so, thenit indicates that at least one external conductive object coupled toground is touching or approaching the touch screen. In an example of thepresent invention, assuming that the signals of the second conductivestrips are S₁, S₂ . . . and S_(n), respectively, and the 1D sensinginformation employs dual differential values, then the values of the 1Dsensing information are ((S₂-S₃)-(S₁-S₂)), ((S₃-S₄)-(S₂-S₃)) . . . and((S_(n-1)-S_(n))-(S_(n-2)-S_(n-1))). In a best mode of the presentinvention, the 1D sensing information employs dual differential values.

Simply put, in the previous examples, a value or a zero-crossing thatexceeds a threshold value can be used to determine if there is at leastone external conductive object coupled to ground touching or approachingthe touch screen. One with ordinary skill in the art can appreciate thatthe 1D sensing information can take forms other than signal values,differential values or dual differential values. For example, each valuecan be the difference between two non-adjacent signal values; thepresent invention is not limited as such.

In a best mode of the present invention, the position detecting devicemust have the ability to simultaneously provide a driving signal to allof the first conductive strips and detect the second conductive strips.That is, during full screen driving, 1D sensing information is producedbased on signals of the second conductive strips. The detection of thesecond conductive strips can be done by scanning conductive strips oneafter the other, scanning some of the conductive strips simultaneously,or scanning all of the conductive strips simultaneously to obtain thesensing information corresponding to all of the second conductivestrips. In the following descriptions, this is referred to as fullscreen driven detection. In other words, full screen driven detectionincludes detecting the mutual capacitive signals of all sensedconductive strips (e.g. all second conductive strips) while all drivenconductive strips (e.g. all first conductive strips) are being driven.

In order to achieve a satisfying resolution, the number of conductivestrips increases with the increase of the size of the touch screen.However, pins used by the controller for simultaneously detecting theconductive strips cannot be necessarily increased accordingly. In 2Dmutual capacitive detection, only conductive strips in a single axisneed to be detected, such as the second conductive strips. Thus, bydirectly using the legacy architecture for detecting the secondconductive strips, the position detecting device only needs to acquiresthe ability of full screen driving in order to perform full screendriven detection. In a preferred example of the present invention, thenumber of the second conductive strips is less than that of the firstconductive strips.

In another example of the present invention, the position detectingdevice must have the ability to simultaneously provide a driving signalto all of the first conductive strips and detect all the conductivestrips. That is, during full screen driving, first 1D sensinginformation is produced based on signals of the first conductive strips,and second 1D sensing information is produced based on signals of thesecond conductive strips. Compared to the previous example, the positiondetecting device must also have the ability to detect the firstconductive strips.

In summary of the above, in full screen driven detection, if there is noapproach or coverage of any external conductive object, regardless ofthe existence of any adhered conductive substances, no real touch willbe determined, that is, the sensing information will not exhibitreal-touch sensing information. In an example of the present invention,the full screen driven detection is used to determine whether there is areal touch or whether there is an approach or coverage by an externalconductive object. In another example of the present invention, the fullscreen driven detection is used to determine the conductive strip(s)touched or covered by the external conductive object, which can be onlythe second conductive strip(s) covered or the first and secondconductive strip(s) covered. In yet another example of the presentinvention, the full screen driven detection is used to determinecoordinates, which can be a 1D coordinate based on 1D sensinginformation, or a first 1D coordinate and a second 1D coordinate (i.e. a2D coordinate) based on the first 1D sensing information and second 1Dsensing information, respectively.

The position detecting device may have the abilities of full screendriven detection and 2D mutual capacitive detection. For example, thedriving signal can be provided simultaneously to all, some or just oneof the first conductive strips, and 1D sensing information or 2D sensinginformation is detected from the second conductive strips.

Referring to FIG. 2E, a flowchart illustrating a full screen drivendetection is carried out followed by a 2D mutual capacitive detectionaccording to a first embodiment of the present invention is shown. Asshown in step 210, a full screen driven detection is carried out togenerate 1D sensing information. Then, as shown in step 220, it isdetermined whether to perform a 2D mutual capacitive detection based onthe 1D sensing information. For example, if the 1D sensing informationdetermines an approach or coverage of an external conductive object,then as shown in step 230, a 2D mutual capacitive detection is carriedout to generate 2D sensing information. Then, as shown in step 240, thelocation of the external conductive object is determined based on the 2Dsensing information.

In step 220, if it is determined that there is no approach or coverageof any external conductive objects, then return to step 210 to repeatthe full screen driven detection. In an example of the presentinvention, the period for performing full screen driven detections isfixed, that is, in a period of time in which a plurality of full screendriven detections are performed consecutively, an interval adjacent twofull screen driven detections is a detection period. In any detectionperiod, if it is determined that there is no approach or coverage of anyexternal conductive objects, then power for performing only one fullscreen driven detection is consumed. Otherwise, power for performing onefull screen driven detection and N times of 1D mutual capacitivedetections (i.e. a 2D mutual capacitive detection) is consumed. Saiddetection period can be adjusted according to needs. For example, undera power saving mode, the duration of the detection period can beprolonged to save power. Under a normal mode, the duration of thedetection period can be shortened to increase detection frequency, thatis, increasing coordinates acquisition rate. In contrast, in anotherexample of the present invention, the detection period is not fixed. Forexample, in step 220, if it is determined that there is no approach orcoverage of any external conductive objects, then return to and repeatstep 210. For example, under a normal mode, unless it is necessary toperform a 2D mutual capacitive detection, full screen driven detectionis repeatedly performed. If it is necessary to perform a 2D mutualcapacitive detection, then step 230 or steps 230 and 240 is/areperformed and then step 210 is repeated.

Moreover, full screen driven detection is carried out based on a firstdetection frequency. After a predetermined period of time or apredetermined number of times has elapsed without any externalconductive object approaching or touching the touch screen, then fullscreen driven detection is carried out based on a second detectionfrequency until approaching or coverage of an external conductive objectis detected. Thereafter, full screen driven detection is again carriedout based on the first detection frequency. For example, the drivingsignal is provided to all of the first conductive strips at a firstfrequency, and since that a predetermined period of time or apredetermined number of times has elapsed without detecting an approachor a touch by any external conductive object coupled to ground, then thedriving signal is provided to all of the first conductive strips at asecond frequency, wherein the first frequency is faster than the secondfrequency. Furthermore, when an approach or a touch of an externalconductive object coupled to ground is detected while the driving signalis provided to all of the first conductive strips at the secondfrequency, the driving signal is then provided to all of the firstconductive strips at the first frequency again.

Alternatively, after the 2D mutual capacitive detection has determinedan approach or coverage of an external conductive object, the 2D mutualcapacitive detection is continued, and steps 210 and 220 are skipped,meaning no full screen driven detection is performed, until the 2Dmutual capacitive detection has not detected any approach or coverage ofexternal conductive objects.

Accordingly, in an example of the present invention, when a drivingsignal is simultaneously provided to all of the first conductive strips,mutual capacitive signals of all of the second conductive strips aredetected to generate 1D sensing information based on the signals of allof the second conductive strips, and it is determined whether a 2Dmutual capacitive detection is to be performed by determining whetherthere is at least one external conductive object coupled to ground isapproaching or touching the touch screen based on the 1D sensinginformation, wherein the 2D mutual capacitive detection is carried outby detecting the mutual capacitive signals of all of the secondconductive strips while a portion of the first conductive strips arebeing provided with the driving signal.

Referring to FIG. 3, a flowchart illustrating the determination oflocations based on results of a full screen driven detection and a 2Dmutual capacitive detection according to a second embodiment of thepresent invention is shown. As shown in step 310, a full screen drivendetection is carried out to generate one or two 1D sensing information.For example, one 1D sensing information is generated based on the firstconductive strips or the second conductive strips, or first 1D sensinginformation corresponding to the first conductive strips and second 1Dsensing information corresponding to the second conductive strips aregenerated based on signals of the first conductive strips and thesignals of the second conductive strips. Next, as shown in step 320, itis determined whether there is an approach or coverage of at least oneexternal conductive object based on the 1D sensing information. If thereis no approach or coverage of an external conductive object, then repeatstep 310; else as shown in step 330, conductive strips approached orcovered by the external conductive object are determined based on the 1Dsensing information, and as shown in step 340, at least one mutualcapacitive detection range is determined based on the conductive stripsapproached or covered by the external conductive object. Then, as shownin step 350, a mutual capacitive detection is performed in the mutualcapacitive detection range to generate 2D sensing information based onmutual capacitive coupling at all intersections within the mutualcapacitive detection range. For example, mutual capacitive coupling atintersections outside the mutual capacitive detection range isdesignated as a predetermined value (e.g. a zero value), in combinationwith values detected from the mutual capacitive coupling within themutual capacitive detection range, 2D sensing information is generated.Thereafter, as shown in step 360, the location of each externalconductive object is determined based on the 2D sensing information.Then, return to repeat step 310. The above 2D sensing information canalso be a partial full screen image, which only shows the capacitivecoupling within the mutual capacitive detection range, and from whichthe location of each external conductive object is further derived.

In an example of the present invention, 1D sensing information isgenerated based on the signals of the first conductive strips, and themutual capacitive detection range is an area that includes allintersections of the first conductive strips approached or covered bythe external conductive object. In other words, a driving signal issequentially provided to the first conductive strips approached orcovered by the external conductive object, and when each firstconductive strip is provided with the driving signal, 2D sensinginformation is generated based on all of the second conductive strips.Compared to 2D full mutual capacitive detection, the present examplesaves a significant amount of time.

In another example of the present invention, 1D sensing information isgenerated based on the signals of the second conductive strips, and themutual capacitive detection range is an area that includes allintersections of the second conductive strips that are approached orcovered by the external conductive object. In other words, a drivingsignal is sequentially provided to the first conductive strips, and wheneach first conductive strip is provided with the driving signal, 2Dsensing information is generated based on the second conductive stripsapproached or covered by the external conductive object. Compared to 2Dfull mutual capacitive detection, the present example ignores noiseoutside the mutual capacitive detection range.

In a preferred example of the present invention, first 1D sensinginformation and second 1D sensing information are generated based on thesignals of the first and second conductive strips, respectively, and themutual capacitive detection range is an area that includes allintersections of the first conductive strips and the second conductivestrips that are approached or covered by the external conductive object.In other words, a driving signal is sequentially provided to the firstconductive strips approached or covered by the external conductiveobject, and when each first conductive strip is provided with thedriving signal, 2D sensing information is generated based on the secondconductive strips approached or covered by the external conductiveobject. Compared to 2D full mutual capacitive detection, the presentexample saves a significant amount of time and ignores noise outside themutual capacitive detection range.

In addition, in an example of the present invention, it can bedetermined whether there is an approach or coverage of at least oneexternal conductive object on the touch screen based on the first 1Dsensing information. This includes: determining a 1D coordinate of eachexternal conductive object coupled to ground based on the first 1Dsensing information; detecting signals of all of the second conductivestrips to obtain a second 1D sensing information generated from thesignals of all of the second conductive strips; determining a second 1Dcoordinate of each external conductive object coupled to ground based onthe second 1D sensing information; forming a 2D coordinate from each 1Dcoordinate and a corresponding second 1D coordinate; using anintersection of a first conductive strip and a second conductive stripclosest to each 2D coordinate as a corresponding detected intersection;and performing mutual capacitive detection at the detected intersectioncorresponding to each 2D coordinate to detect a mutual capacitive signalat the intersection corresponding to each 2D coordinate in order todetermine a 2D coordinate for each external conductive object coupled toground.

The mutual capacitive detection for any detected intersection mayinclude providing a driving signal to at least one first conductivestrip including the one intersected at the detected intersection, anddetecting a signal of the second conductive strip intersected at thedetected intersection, so as to detect a mutual capacitive signal ateach intersection, wherein intersections on the same first conductivestrip can be simultaneously detected while the driving signal isprovided to at least one first conductive strip including the oneintersected at the detected intersection, wherein the signal of the 2Dcoordinate of an external conductive object coupled to ground exceeds athreshold.

In another example of the present invention, it can be determined ifthere is an external conductive object coupled to ground approaching ortouch the touch screen based on the first 1D sensing information and/orthe second 1D sensing information. This includes: determining a mutualcapacitive detection range based on the first 1D sensing information orbased on the first 1D sensing information and the second 1D sensinginformation; performing mutual capacitive detection in this mutualcapacitive detection range to generate a 2D sensing information based onmutual capacitive signals at the intersections of all of the first andsecond conductive strips in the mutual capacitive detection range; anddetermining the location of each external conductive object coupled toground based on the 2D sensing information.

The above mutual capacitive detection range can be determined by allintersections of the first and the second conductive strips on the firstconductive strips touched or approached by any external conductiveobject coupled to ground or determined by all intersections of the firstand the second conductive strips touched or approached by any externalconductive object coupled to ground determined based on the first 1Dsensing information or based on the first 1D sensing information and thesecond 1D sensing information.

Referring to FIG. 4A, a flowchart illustrating the determination oflocations based on results of a full screen driven detection and amutual capacitive detection according to a third embodiment of thepresent invention is shown. As shown in step 410, a full screen drivendetection is carried out to generate one 1D sensing information. Next,as shown in step 420, it is determined whether there is an approach orcoverage of at least one external conductive object based on the 1Dsensing information. If there is no approach or coverage of an externalconductive object, then repeat step 410; else as shown in step 430, atleast a first 1D coordinate is determined based on the 1D sensinginformation. Then, as shown in step 440, at least a first mutualcapacitive detection range is determined based on at least oneconductive strip corresponding to the first 1D coordinate. Then, asshown in step 450, a mutual capacitive detection is performed in thefirst mutual capacitive detection range to determine at least a second1D coordinate corresponding to each first 1D coordinate. For example,two first 1D coordinates are determined in step 430, and in step 440,two mutual capacitive detection ranges are determined based on twoconductive strips closet to the two first 1D coordinates, and in step450, a mutual capacitive detection is performed to generate 1D sensinginformation corresponding to each of the first 1D coordinates, and atleast a second 1D coordinate is determined corresponding to each of thefirst 1D coordinates. The first 1D coordinate and the second 1Dcoordinate can form a 2D coordinate, for example, (first 1D coordinate,second 1D coordinate) or (second 1D coordinate, first 1D coordinate).

For example, while the driving signal is provided to the firstconductive strips, all of the second conductive strips are detected toobtain a first 1D sensing information generated based on the signals ofall of the second conductive strips. In addition, determining whetherthere is an external conductive object coupled to ground touch orapproaching the touch screen based on 1D sensing information can furtherinclude: determining at least a first 1D coordinate based on the first1D sensing information; determining a first mutual capacitive detectionrange based on each first 1D coordinate, and performing mutualcapacitive detection in the first mutual capacitive detection range togenerate a second 1D sensing information corresponding to each first 1Dcoordinate; generating at least a second 1D coordinate corresponding toeach first 1D coordinate based on the second 1D sensing information ofeach first 1D coordinate; and generating a 2D coordinate based on eachfirst 1D coordinate and each corresponding second 1D coordinate.

Referring to FIG. 4B, a step 460 is further included, in which at leasta second mutual capacitive detection range is determined based on thesecond 1D coordinate, and a step 470 is further included, in which amutual capacitive detection is performed in the second mutual capacitivedetection range to determine a third 1D coordinate corresponding to eachsecond 1D coordinate. The second 1D coordinate and the third 1Dcoordinate can form a 2D coordinate, for example, (third 1D coordinate,second 1D coordinate) or (second 1D coordinate, third 1D coordinate).

For example, while the driving signal is provided to the firstconductive strips, all of the second conductive strips are detected toobtain a first 1D sensing information generated based on the signals ofall of the second conductive strips. In addition, determining whetherthere is an external conductive object coupled to ground touch orapproaching the touch screen based on 1D sensing information can furtherinclude: determining at least a first 1D coordinate based on the first1D sensing information; determining a first mutual capacitive detectionrange based on each first 1D coordinate, and performing mutualcapacitive detection in the first mutual capacitive detection range togenerate a second 1D sensing information corresponding to each first 1Dcoordinate; generating at least a second 1D coordinate corresponding toeach first 1D coordinate based on the second 1D sensing information ofeach first 1D coordinate; determining a second mutual capacitivedetection range based on each second 1D coordinate, and performingmutual capacitive detection in the second mutual capacitive detectionrange to generate a third 1D sensing information corresponding to eachsecond 1D coordinate; generating at least a third 1D coordinatecorresponding to each second 1D coordinate based on the third 1D sensinginformation of each second 1D coordinate; and generating a 2D coordinatebased on each second 1D coordinate and each corresponding third 1Dcoordinate.

In FIG. 4A, each first 1D coordinate matching each corresponding second1D coordinate represent the location of an external conductive objects.In addition, when the external conductive object is determined, returnto repeat step 410. In FIG. 4B, each second 1D coordinate matching eachcorresponding third 1D coordinate represent the location of an externalconductive object. In addition, when the external conductive object isdetermined, return to repeat step 410.

Referring to FIG. 4C, a flowchart illustrating the determination oflocations based on results of a full screen driven detection and amutual capacitive detection according to a third embodiment of thepresent invention is shown. As shown in step 410, a full screen drivendetection is carried out to generate two 1D sensing information. Next,as shown in step 420, it is determined whether there is an approach orcoverage of at least one external conductive object based on the 1Dsensing information. If there is no approach or coverage of an externalconductive object, then repeat step 410; else as shown in step 480,every possible 2D coordinate is determined based on the 1D sensinginformation, and at least a mutual capacitive detection range isdetermined based on the 2D coordinate. Then, as shown in step 490, a 2Dcoordinate corresponding to a real touch is determined based on themutual capacitive detection range.

It is apparent that with the above full screen driven detectiontechnique, an approach or touch of an external conductive object coupledto external ground can be successfully determined regardless of whetherthere is any water stain or other conductive objective that is notcoupled to ground. Furthermore, when an approach or touch of an externalconductive object coupled to external ground is detected, through the 2Dmutual capacitive detection, the range to which a water stain or otherconductive object not coupled to external ground adheres other than therange in which an external conductive object coupled to ground touchesor approaches can be determined. When the range to which a water stainor other conductive object not coupled to external ground adheres isdetermined, no coordinate of this detected range to which the waterstain or other conductive object not coupled to external ground adherescan be provided, or a message or signal for cleaning of the touch screensurface can be displayed, indicating the interference of any water stainor other conductive object not coupled to ground is eliminated.

In another example of the present invention the 2D mutual capacitivedetection is performed before the full screen driven detection isperformed. The full screen driven detection can determine an conductivestrip touched or approached by an external conductive object coupled toexternal ground, and when compared with the 2D sensing informationgenerated from the 2D mutual capacitive detection, the range to which awater stain or other conductive object not coupled to external groundadheres other than the range in which an external conductive objectcoupled to ground touches or approaches can be determined.

During system operation, the influence and interference of the externalenvironment on the touch screen may constantly be varying, and in orderto adept to such variations, the reference values can be updatedperiodically or non-periodically. Thus, update of the reference valuescan be performed continuously, or during the processes of full screendriven detection and/or mutual capacitive detection.

During mutual capacitive detection, if there is a conductive substanceadhered to the touch screen, the 2D sensing information will exhibit acorresponding unreal touch or an unreal touch surrounded by a realtouch. At this time, if the reference values are updated, then they willinclude the unreal touch. Before the next update of the referencevalues, as long as the external conductive object is not at the areawhere the unreal touch is, determination of the locations of externalconductive object can be made correctly. However, if the conductivesubstance is removed, then the area that exhibits the unreal touch inthe original reference will cause a real touch to be determined in the2D sensing information, leading to a misjudgment.

By comparing with 1D sensing information generated in the above fullscreen driven detection, non-matching real touches exist between the 2Dsensing information and the 1D sensing information, which reflects theabove problem, and update of the reference values for mutual capacitivedetection is performed to resolve the problem. For example, the 2Dsensing information is 1D projected to generate 1D sensing information,or values corresponding to intersections on each second conductive stripare summed up to generate 1D sensing information. The 1D sensinginformation derived from the 2D sensing information is used forcomparison with the 1D sensing information produced in full screendriven detection, so as to determine any non-matching real touches andwhether update of the reference values for mutual capacitive detectionshould be performed in advance.

In addition, it is possible to determine whether a conductive substanceis adhered to the touch screen solely by 2D full mutual capacitivedetection. For example, in the case that 2D sensing information exhibitsonly unreal touch but no real touch or exhibits real touch that onlyappears in proximity to the unreal touch and no real touch that exceedsa certain threshold, then it can be determined that a conductivesubstance may be adhered to the touch screen. In an example of thepresent invention, one can presume that a conductive substance isattached to the touch screen. In another example of the presentinvention, another full screen driven detection can be carried out toascertain if there is an approach or coverage by an external conductiveobject.

In an example of the present invention, update of the reference valuesis made when there is no approach or coverage of the touch screen madeby any external conductive object. For example, as mentioned before, afull screen driven detection is firstly used to determine if there is anexternal conductive object approaching or covering the touch screen.When there is no approach or coverage of the touch screen made by anyexternal conductive object, update of the reference values is made,which may include the reference update for the full screen drivendetection and/or the mutual capacitive detection. As another example,the 2D sensing information generated by the 2D full mutual capacitivedetection is used to determine if there is an external conductive objectapproaching or covering the touch screen. When there is no approach orcoverage of the touch screen made by any external conductive object,update of the reference values is made.

Referring to FIG. 5A, a flowchart illustrating a way of updatingreference values proposed in accordance with a fourth embodiment of thepresent invention is shown. Compared with FIG. 2E, the method furtherincludes, as shown in step 250, determining whether there has been notouch or approach of any external conductive object coupled to ground onthe touch screen for a predetermined period of time based on the 1Dsensing information. If not, then as shown in step 210, full screendriven detection is performed. Otherwise, if it is determined that therehas been no touch or approach of any external conductive object coupledto ground on the touch screen for a predetermined period of time basedon the 1D sensing information, then as shown in steps 260 and 270, a 2Dmutual capacitive detection is performed obtain a 2D sensinginformation, and reference values are updated based on the 2D sensinginformation. The steps of updating a reference in FIG. 5A can be carriedout by the above controller 160. In an example of the present invention,updating the reference values based on the 2D sensing informationincludes using the 2D sensing information as the new reference values orusing an average of the 2D sensing information and the originalreference values as the new reference values. Moreover, the location ofeach external conductive object coupled to ground is determined from theamount of change between mutual capacitive signals of the 2D sensinginformation and the reference values.

For example, a device for detecting a touch screen in accordance withthe present invention includes: the touch screen including a pluralityof first conductive strips and a plurality of second conductive strips;and a controller for performing a full screen driven detection, whichincludes: simultaneously providing a driving signal to all of the firstconductive strips; when all of the first conductive strips are providedwith the driving signal, detecting mutual capacitive signals of all ofthe second conductive strips to generate a one-dimensional (1D) sensinginformation based on the signals of all of the second conductive strips;and determining whether at least one external conductive object coupledto ground is touching or approaching the touch screen based on the 1Dsensing information; and when the controller determining the touchscreen is not touched or approached by any external conductive objectover a predetermined period of time based on the 1D sensing information,performing a 2D mutual capacitive detection to obtain a 2D sensinginformation to update reference values based on the 2D sensinginformation, wherein the 2D mutual capacitive detection includes:sequentially providing a driving signal to one or more differentconductive strips in the first conductive strips, and providing a DCpotential to all of the guarding conductive strips; each time one ormore different conductive strips in the first conductive strips beingprovided with the driving signal, detecting the signals of all of thesecond conductive strips to obtain a 1D sensing informationcorresponding to the one or more first conductive strips being providedwith the driving signal generated based on the mutual capacitive signalsof all of the second conductive strips; and combining each 1D sensinginformation corresponding to the one or more first conductive stripsbeing provided with the driving signal to generate a 2D sensinginformation.

When determining the touch screen is touched or approached by at leastone external conductive object coupled to ground based on the 1D sensinginformation, a 2D mutual capacitive detection is performed to obtain a2D sensing information, and the location of each external conductiveobject coupled to ground is determined based on the 2D sensinginformation.

In the case that the touch screen is provided in a handheld device, itis likely that a hand holding the handheld device is approaching orcovering the touch screen while turning on the device. If referenceupdate is performed at this moment, then the initial reference valueswill include real-touch sensing information, such that the area in whichthe real-touch sensing information resides in the reference valuescannot correctly reflect an approach or coverage by an externalconductive object. Even if the hand (or finger) causing the real-touchsensing information later moves away from the touch screen, it may stillprevent this area from reflecting an approach or coverage by an externalconductive object, e.g. the location of an external conductive objectapproaching or covering this area cannot be determined correctly.

Referring to FIG. 5B, a flowchart illustrating a way of updating thereference values according to a fifth embodiment of the presentinvention is shown. The present invention proposes pre-storing originalreference values. The original reference values can be stored in anon-volatile storage unit that retains data even if power is off. First,as shown in steps 510 and 520, the original reference values DS arecompared with obtained reference values IS to see if they match eachother. If yes, then as shown in step 530, normal operations areperformed; else as shown in step 540, the original reference values arecompared with obtained sensing information (1D sensing information or 2Dsensing information) to see if they match each other, if not, then asshown in step 560, normal operations are performed; else as shown instep 550, the reference values are updated.

Under normal circumstances, the reference values are updated when thereis no external conductive object approaching or covering the touchscreen or no conductive substance attached to the touch screen, sonormal reference values (including the original reference values DS)obtained should not exhibit any real or unreal touches. Assuming theoriginal reference values DS are normal, and there is an externalconductive object approaching or covering when the reference values ISare updated, afterwards when the sensing information RS is obtained, theoriginal reference values DS are compared with the reference values IS,at this time they won't match. Thus, the sensing information RS iscompared with the reference values DS, if they match, then it meansthere is no external conductive object approaching or covering thetemperature or no conductive substance attached to the touch screen, soupdate of the reference values IS can be performed immediately. If theydo not match each other, update of the reference values IS is notpermitted, and normal operations are performed. For example, when a handpresses against the touch screen during power-on of the device, not onlythe reference values exhibit a real touch, the subsequent sensinginformation RS also exhibits a real touch. These two are the same, soeven if the hand presses against the touch screen, no approach orcoverage by an external conductive object is determined, thus ignoringthe existence of the portion pressed by the hand while the device isbeing turned on. However, other parts of the touch screen may stilloperate normally. Once this hand moves away, if other portions have noapproaching or touching external conductive object, in step 540, it isdetermined that the sensing information RS and the original referencevalues DS match each other, so update of the reference values can bemade. If in step 540, other portions still have approaching or touchingexternal conductive objects, then normal operations are performed, andupdate of the reference values IS is made when there is no approach orcoverage made by any external conductive objects. In addition, if theoriginal reference values are not normal, then the sensing informationRS and the original reference values DS will not match each other, sonormal operations are performed as shown in step 560.

The above reference values are applicable to self capacitive detection,mutual capacitive detection or full screen driven detection.

Moreover, the update of the reference values may be an update of aportion or all of the reference values. As described earlier, selfcapacitive detection and full screen driven detection generate 1Dsensing information. When this is used as the reference values, then theupdate of the reference values means an update of all the referencevalues. During mutual capacitive detection, 2D sensing information is acollection of 1D sensing information corresponding to each firstconductive strip (the first conductive strip provided with a drivingsignal), so the update of the reference values may be an partialreference update for a just one of the first conductive strips, in otherwords, an update of only one of a plurality of 1D sensing information inthe reference values.

The touch screen of the present invention can be used for transmittingand receiving information, that is, the touch screen can be used forcapacitive communication. With the controller providing a driving signalto one, some or all of the first conductive strips on the touch screen,signals can be transmitted. With the controller detecting one, some orall of the second conductive strips, signals can be received, so twotouch screens may carry out one-way or two-way communications.

In an example of the present invention, touch screens can communicatewith each other face to face, that is, touch screens carry outcapacitive communication face to face with insulating surface layerstherebetween. For example, touch screens may perform capacitivecommunication through human body. For example, one hand of a usertouches the touch screen of a handheld device, while the other handtouches the touch screen of another handheld device, using the humanbody is a conductive medium for capacitive communication. As anotherexample, a first user and a second user touch the touch screens of afirst and a second handheld device, respectively. When the first userand the second user have body contact, the touch screens of the firstand second handheld devices may then perform capacitive communication.One with ordinary skill in the art can appreciate that capacitivecommunication is not limited to one-to-one communication, but may bemany-to-many communication, and the conductive medium is not limited tohuman body, but may be other conductive media. For example, two touchscreens can reside in pockets of two different people. When these peopleshake hands or make contact with each other, these two touch screens cancarry out communication.

Accordingly, a method for communication through touch screens isproposed by the present invention, which uses a first touch screen and asecond touch screen for communication. The first and second touchscreens have a detecting mode for detecting an approach or a touch of anexternal conductive object. In addition, the first and second touchscreens further have a communication mode for communicating throughcapacitive coupling between the first and second touch screens in orderto exchange or communicate a message. Therefore, a communication systemis formed by the first and second touch screens. In an example of thepresent invention, the detecting and the communication modes can beexecuted in turns. In another example of the present invention, a userinterface can be employed to switch between the detecting and thecommunication modes.

Referring to FIG. 6, a flowchart illustrating a method for communicationthrough touch screens according to a sixth embodiment of the presentinvention is shown. As shown in step 610, a first touch screen and asecond touch screen are provided. Then, in steps 620 and 630, whetherthere is an approach or a touch of an external conductive object isindividually determined during a detecting mode of the first and thesecond touch screens, and capacitively coupled communication between thefirst and the second touch screens are performed during a communicationmode of the first and the second touch screens in order to exchange orcommunicate a message.

For example, the first touch screen has a transparent insulating layerand a conductive layer. The message is transmitted by capacitivecoupling from the conductive layer to the second touch screen with thetransparent insulating layer disposed in between. On the other hand, thesecond touch screen also has a transparent insulating layer and aconductive layer. The message is transmitted by capacitive coupling fromits conductive layer to the first touch screen with the transparentinsulating layer disposed in between. The capacitive coupling betweenthe first and the second touch screens can be a capacitive couplingbetween the first touch screen and the second touch screen through acapacitive coupling between the first touch screen and at least anexternal conductive object. For example, the first and the second touchscreens both have a plurality of first conductive strips that will beprovided with a driving signal during the detecting mode and a pluralityof second conductive strips that will provide capacitive signals as aresult of the driving signal. In the communication mode, the first andthe second touch screens may communicate with each other by a firstconductive strip and/or a second conductive strip touched or approachedby an external conductive object.

Signals can be transmitted in analog or digital form. In a preferredexample of the present invention, signals are sent in the form ofdigital encoding. For example, they can be in the form of binary stringsor packets. The number of bits for a single transmission may be fixed orvariable, such as a balanced code or Berger code with a fixed length.Signals may also be in the form of packets with packet headers.Capacitive communication may employ handshaking mechanism as atransmission requirement by a touch screen at the transmitter endsending encoded signals or packets, so that a touch screen at thereceiver end may acknowledge by returning a signal or packet in responseto a successful reception of the transmission, thereafter the touchscreen at the transmitter end may start transmitting data to thereceiver end.

When two touch screens face each other in close proximity or touch eachother, one touch screen may know of the existence of the other touchscreen by providing a driving signal to conductive strips and detectingsignals from conductive strips, and may then perform capacitivecommunication. In an example of the present invention, a first touchscreen may provide the driving signal, and if a second touch screentouches the first touch screen or is within a predetermined range,signals of conductive strips of the first touch screen will be smallerthan signals of the conductive strips of the first touch screen when thesecond touch screen is not touching or within the predetermine distance,thereby confirming whether capacitive communication can be carried out.At the same time, conductive strips of the second touch screen will alsobe affected by the capacitive coupling of the driving signal of thefirst touch screen, so confirmation of whether capacitive communicationis allowed can also be made by detecting the conductive strips of thesecond touch screen.

In an example of the present invention, the controller that performscapacitive communication has the ability of identifying the conductivestrips that are receiving signals. For example, when a first or a firstgroup of transmitting conductive strip(s) of the first touch screenis/are driven by driving signal(s), a first or a first group ofreceiving conductive strip(s) of the second touch screen is/arecapacitively coupled. When the controller of the second touch screendetects signals of the various conductive strips, it may identify theconductive strips that are capacitively coupled. In this case, thesecond touch screen may select one or some conductive strips as a secondor a second group of transmitting conductive strip(s) except for theidentified first or first group of receiving conductive strip(s), andprovide a driving signal thereto. Similarly, the first touch screen mayidentify a second or a second group of receiving conductive strip(s)that are capacitive coupled with the driving signal provided by thesecond touch screen. In other words, the capacitive communicationsperformed by the touch screens of the present invention can be simplexor full duplex. Since the touch screens may not exactly aligned witheach other when placed face-to-face, and the size or the number ofconductive strips of the first and second touch screens may not be thesame, the capacitive communications performed by the touch screens ofthe present invention are applicable to touch screens that are notaligned or with different sizes or different number of conductivestrips.

The types of communications of the touch screens in the presentinvention may include, but not limited to, simplex, half duplex or fullduplex. The capacitive coupling between the first and the second touchscreens is a direct capacitive coupling between the first and the secondtouch screens facing each other, wherein the areas of the first and thesecond touch screens facing each other include a first area and a secondarea. The first and the second touch screens perform half-duplex orfull-duplex communications through capacitive coupling between the firstand the second areas. In an example of the present invention, the firstand the second touch screens both have a plurality of conductive strips.The conductive strips in the first area of the first touch screen do notoverlap with the conductive strips in the second area of the secondtouch screen.

The one or more transmitting conductive strips and the corresponding oneor more receiving conductive strips of the first and second touchscreens can be referred to as a group of communicating conductivestrips. In an example of the present invention, the capacitivecommunications performed by the touch screens of the present inventioncan distinguish several groups of communicating conductive strips. Theycan perform capacitive communications simultaneously, thus carrying outmultiple-bit parallel communications or multiple-group serialcommunications. In an example of the present invention, dual-railcommunications can be performed by two groups of communicatingconductive strips, in which only one group of a first group ofcommunicating conductive strips and a second group of communicatingconductive strips are transmitting signals at one time. For example, a‘1’ value is used to represent the case when the first group ofcommunicating conductive strips are transmitting signals, and a ‘0’value is used to represent the case when the second group ofcommunicating conductive strips are transmitting signals, so that propertransmissions of the signals are ensured.

Moreover, the first touch screen may first detect the portion of thetouch screen approached or covered by a hand, and then provide a drivingsignal to one or more conductive strips approached or covered by theconductive medium for transmitting signals, this saves more powercompared to full screen driving. Similarly, the second touch screen mayfirst detect the portion of the touch screen approached or covered by aconductive medium, and receive signals through the one or moreconductive strips covered by the conductive medium.

One with ordinary skill in the art can appreciate that the capacitivecommunications performed by the touch screens of the present inventioncan be used for transmitting audio data, image data, text data, command,or other information, and are not limited to just handheld devices, butespecially applicable to mobile phones, tablets, touch pads, or otherdevices with touch screen(s). In addition, the aforementioned touchscreens are not limited to projected capacitive touch screens, but mayalso be surface capacitive touch screens, resistive touch screens andthe like. For example, the first touch screen performing communicationas mentioned before is a surface capacitive touch screen, and the secondtouch screen is a projected capacitive touch screen.

Referring to FIG. 7, a schematic diagram depicting performingcommunication using touch screens proposed by a seventh embodiment ofthe present invention is shown. While a capacitive touch screen isprovided with a driving signal, a ground potential of a first touchscreen 71 is provided to at least one conductive strip 73 of the firsttouch screen 71, and a ground potential of a second touch screen 72 isprovided to at least one conductive strip 74 of the second touch screen72, such that the conductive strips of the first touch screen 71 and thesecond touch screen 72 being provided with the ground potentials arecapacitively coupled with each other, thereby reducing the difference inground potentials between the first and the second touch screens.

For example, conductive strips of the first touch screen arranged in afirst direction are provided with a driving signal, and conductivestrips thereof arranged in a second direction are provided with theground potential, whereas conductive strips of the second touch screenarranged in a first direction are provided with the ground potential,and conductive strips thereof arranged in a second direction are usedfor detecting transmitted data. As another example, a plurality ofconsecutively arranged conductive strips of the first touch screen areprovided with the driving signal, while the rest of the conductivestrips are provided with the ground potential, whereas conductive stripsof the second touch screen not used for detecting signals are providedwith the ground potential.

In a preferred mode of the present invention, the first touch screen hasthe abovementioned guarding conductive strips, and these guardingconductive strips are provided with the ground potential.

In an example of the present invention, which is in step 630 above,during communication, at least a portion of the first touch screen andat least a portion of the second touch screen are provided with a groundpotential, respectively, and these portions of the first and the secondtouch screen being provided with the ground potentials are capacitivelycoupled with each other face-to-face, such that the ground potentials ofthe first and the second touch screens can be made closer to each other.The capacitive coupling between the first and the second touch screensis a direct capacitive coupling between the first and the second touchscreens facing each other, wherein the areas of the first and the secondtouch screens facing each other include a first area and a second area.The first and the second touch screens perform half-duplex orfull-duplex communications through the capacitive coupling in the firstand the second areas.

In a first example of the present invention, the first and the secondtouch screens both have a plurality of first conductive strips that willbe provided with the driving signal during the detecting mode and aplurality of second conductive strips that will provide capacitivesignals as a result of the driving signal. The first conductive stripsare those performing the communications in the first and the secondareas, and the second conductive strips are provided with the groundpotentials during the detecting mode.

In a second example of the present invention, the first and the secondtouch screens both have the plurality of first conductive strips thatwill be provided with a driving signal during the detecting mode and aplurality of second conductive strips that will provide capacitivesignals as a result of the driving signal. The second conductive stripsare those performing the communications in the first and the secondareas, and the first conductive strips are provided with the groundpotentials during the detecting mode.

In a third example of the present invention, the first and the secondtouch screens both have a plurality of first conductive strips that willbe provided with the driving signal during the detecting mode and aplurality of second conductive strips that will provide capacitivesignals as a result of the driving signal, and the areas of the firstand the second touch screens facing each other further include a thirdarea. The second conductive strips are those performing thecommunications in the first and the second areas, and the secondconductive strips in the third area are provided with the groundpotentials during the detecting mode.

In a fourth example of the present invention, the first and the secondtouch screens both have a plurality of first conductive strips that willbe provided with the driving signal during the detecting mode and aplurality of second conductive strips that will provide capacitivesignals as a result of the driving signal, wherein during thecommunication mode, one of the first conductive strips and one of thesecond conductive strips are simultaneously provided with the drivingsignal, and another of the first conductive strips and another of thesecond conductive strips are simultaneously provided with the groundpotentials.

The above embodiments are only used to illustrate the principles of thepresent invention, and they should not be construed as to limit thepresent invention in any way. The above embodiments can be modified bythose with ordinary skill in the art without departing from the scope ofthe present invention as defined in the following appended claims.

1. A method for detecting a touch screen comprising: providing the touch screen including a plurality of first conductive strips and a plurality of second conductive strips; performing a full screen driven detection including: simultaneously providing a driving signal to all of the first conductive strips; when all of the first conductive strips are provided with the driving signal, detecting mutual capacitive signals of all of the second conductive strips to generate a one-dimensional (1D) sensing information based on the signals of all of the second conductive strips; and determining whether at least one external conductive object coupled to ground is touching or approaching the touch screen based on the 1D sensing information; and when determining the touch screen is not touched or approached by any external conductive object over a predetermined period of time based on the 1D sensing information, performing a 2D mutual capacitive detection to obtain a 2D sensing information, and updating reference values based on the 2D sensing information, wherein the 2D mutual capacitive detection includes: sequentially providing a driving signal to one or more different conductive strips in the first conductive strips; each time one or more different conductive strips in the first conductive strips being provided with the driving signal, detecting the signals of all of the second conductive strips to obtain a 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal generated based on the mutual capacitive signals of all of the second conductive strips; and combining each 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal to generate a 2D sensing information.
 2. The method of claim 1, wherein when determining the touch screen is not touched or approached by any external conductive object for the predetermined period of time based on the 1D sensing information, a 2D mutual capacitive detection is performed to obtain a 2D sensing information, and a location of each external conductive object coupled to ground is determined based on the 2D sensing information.
 3. The method of claim 1, wherein a location of each external conductive object coupled to ground is determined from the amount of change between mutual capacitive signals of the 2D sensing information and the reference values.
 4. The method of claim 1, wherein updating the reference values based on the 2D sensing information includes using the 2D sensing information as the new reference values or using an average of the 2D sensing information and the original reference values as the new reference values.
 5. The method of claim 1, wherein the driving signal is provided to all of the first conductive strips at a first frequency, and when the touch screen is not touched or approached by any external conductive object coupled to ground for a predetermined period of time or a predetermined number of times since providing the driving signal to all of the first conductive strips at the first frequency, the driving signal is provided to all of the first conductive strips at a second frequency instead, wherein the first frequency is faster than the second frequency.
 6. The method of claim 5, wherein when an approach or a touch of an external conductive object coupled to ground on the touch screen is determined while all of the first conductive strips are provided with the driving signal at the second frequency, the driving signal is provided to all of the first conductive strips at the first frequency again.
 7. The method of claim 1, wherein the touch screen includes an insulating surface layer, a first sensing layer including the first conductive strips, an insulating layer, and a second sensing layer including the second conductive strips.
 8. The method of claim 1, wherein the touch screen is a rectangle including two opposite long sides and two opposite short sides, wherein the first conductive strips are arranged in parallel with the two opposite short sides, and the second conductive strips are arranged in parallel with the two opposite long sides.
 9. A device for detecting a touch screen in accordance with the present invention includes: the touch screen including a plurality of first conductive strips and a plurality of second conductive strips; and a controller for performing a full screen driven detection, including: simultaneously providing a driving signal to all of the first conductive strips; when all of the first conductive strips are provided with the driving signal, detecting mutual capacitive signals of all of the second conductive strips to generate a one-dimensional (1D) sensing information based on the signals of all of the second conductive strips; and determining whether at least one external conductive object coupled to ground is touching or approaching the touch screen based on the 1D sensing information; and when the controller determining the touch screen is not touched or approached by any external conductive object over a predetermined period of time based on the 1D sensing information, performing a 2D mutual capacitive detection to obtain a 2D sensing information to update reference values based on the 2D sensing information, wherein the 2D mutual capacitive detection includes: sequentially providing a driving signal to one or more different conductive strips in the first conductive strips, and providing a DC potential to all of the guarding conductive strips; each time one or more different conductive strips in the first conductive strips being provided with the driving signal, detecting the signals of all of the second conductive strips to obtain a 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal generated based on the mutual capacitive signals of all of the second conductive strips; and combining each 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal to generate a 2D sensing information.
 10. The device of claim 9, wherein when determining the touch screen is not touched or approached by any external conductive object for the predetermined period of time based on the 1D sensing information, a 2D mutual capacitive detection is performed to obtain a 2D sensing information, and a location of each external conductive object coupled to ground is determined based on the 2D sensing information.
 11. The device of claim 9, wherein a location of each external conductive object coupled to ground is determined from the amount of change between mutual capacitive signals of the 2D sensing information and the reference values.
 12. The device of claim 9, wherein updating the reference values based on the 2D sensing information includes using the 2D sensing information as the new reference values or using an average of the 2D sensing information and the original reference values as the new reference values.
 13. The device of claim 9, wherein the driving signal is provided to all of the first conductive strips at a first frequency, and when the touch screen is not touched or approached by any external conductive object coupled to ground for a predetermined period of time or a predetermined number of times since providing the driving signal to all of the first conductive strips at the first frequency, the driving signal is provided to all of the first conductive strips at a second frequency instead, wherein the first frequency is faster than the second frequency.
 14. The device of claim 13, wherein when an approach or a touch of an external conductive object coupled to ground on the touch screen is determined while all of the first conductive strips are provided with the driving signal at the second frequency, the driving signal is provided to all of the first conductive strips at the first frequency again.
 15. The device of claim 9, wherein the touch screen includes an insulating surface layer, a first sensing layer including the first conductive strips, an insulating layer, and a second sensing layer including the second conductive strips.
 16. The device of claim 9, wherein the touch screen is a rectangle including two opposite long sides and two opposite short sides, wherein the first conductive strips are arranged in parallel with the two opposite short sides, and the second conductive strips are arranged in parallel with the two opposite long sides. 